This invention relates to a data transmission system including data transmission links and a plurality of stations connected to the transmission links, and more particularly to the data transmission system wherein each station operates to monitor and accumulate states of other stations. This operation is termed a trace performance.
One example of a prior art data transmission system having a trace performance is disclosed in U.S. Pat. No. 4,335,426.
In the prior art data transmission system, since each station contains a program for tracing (tracer) which is not required to be used usually, the performance for the processes which are usually executed is decreased proportionally. Where a read only memory (ROM) device is used for storing the processing programs, as the trace performance is not included, it is impossible that a user can take out a trace information of a specific system state during operation or maintenance at any time desired.